Intake manifolds for automotive engines typically are comprised of a plenum or chamber having an open end and an opposite closed end and defining a plurality of outlet holes therebetween. The intake manifold also includes a plurality of tubes having first ends joined with the outlet holes of the plenum and opposite second ends connected with associated holes of a flange member which is adapted for mounting to a cylinder head of an engine.
Intake manifolds are traditionally produced entirely by casting These castings are fairly heavy and add undesirable weight to a vehicle Furthermore, since the tubes are usually U-shaped, the manifold cannot be cast in one piece but rather must be cast in two sections, with one section comprising a length of the tubing cast integrally with the plenum and the other section comprising the remaining length of the tubing cast integrally with the flange member. The halves must then be joined together with bolts and a gasket or other suitable hardware to complete the manifold, further adding to the cost, weight and complexity of the manifold.
The U.S. Pat. Nos. 4,829,944, granted May 16, 1989 and 4,887,557, granted Dec. 19, 1989, both in the name of Sukimoto et al., disclose an intake manifold in which the tubes are formed separately from the plenum and flange members out of wrought aluminum The tubes then are joined to the plenum and flange members by a furnace brazing process. Although this type of intake manifold is lighter weight and more aesthetically pleasing than the traditional all-cast type manifolds, it is deficient in that brazed joints are employed.
Brazing employs a brass filler material (i.e., a copper based alloy having zinc or zinc and silver as the alloyant) and is performed at temperatures exceeding 1100.degree. F. Such high temperature brazing processes are costly and present problems of dimension control of the tubes, plenum and flange as these pieces are being joined Furthermore, brazed joints have a tendency to crack over an extended period of time as they are subjected to thermal cycling during normal use.